By the very nature of their operation, internal combustion engines produce relatively high temperatures as a result of the combustion of an air/fuel mixture within the engine. These temperatures are normally kept at a manageable level by an engine cooling system which transfers a portion of this heat of combustion to the surrounding environment in order to cool the engine. Typically, this cooling system is in the form of a continuously circulating fluid coolant which is passed through a heat exchanging radiator in order to remove a portion of the heat from the engine. Such cooling systems normally cease to operate upon engine shutdown.
In many engines, particularly in turbocharged engines, critical stress can be placed upon certain engine components, such as the turbocharger and exhaust manifold, when the engine is operated under a heavy load and then shutdown without an adequate cooling off period. Operation of the engine at high load results in more air/fuel mixture being burned within the engine, thereby generating more heat to be dissipated. The engine therefore elevates in temperature, particularly the exhaust manifold which is used to evacuate the hot combustion exhaust gases, and the turbocharger, which is driven by all or a portion of the these exhaust gases.
At elevated temperatures produced by heavy load conditions in the engine, discontinuation of cooling at engine shutdown will allow the exhaust manifold and turbocharger to continue to increase in temperature for a time prior to cooling off to ambient temperature conditions. This is particularly troublesome for the turbocharger bearings, which will spin at vary high rpms (up to 100,000 rpm) for several minutes after the engine has shutdown with no cooling being applied thereto. Such hot engine shutdowns therefore greatly shorten the life of these components and comprise a major maintenance concern for such engines.
This problem is further compounded by the fact that most trucks having heavy duty turbocharged diesel engines are not driven by the owners of the trucks. There is therefore often not any economic incentive for the driver to follow the proper procedure for cooling off an engine prior to engine shutdown after heavy load operating conditions There is therefore a need for a method for determining if an engine is being shutdown prematurely during high temperature conditions, such that corrective actions may be taken in the future. There is also a need for a method for determining if prior hot engine shutdowns are likely responsible for current engine malfunctions. The present invention is directed toward meeting these needs.